QSFP-4SFP25G-CUxM-BCC | Dell Compatible 100GB QSFP to 4 x 25GB SFP25G Direct Attach Breakout Cable | 1M to 5M

Q: Will this work in place of the Dell DAC-QSFP-4SFP28-25G2M?
A: Yes. This cable is coded for Dell compatibility and conforms to the same IEEE 802.3bj 100GBASE-CR4 and 25GBASE-CU standards, SFF-8665 QSFP28, and SFF-8402 SFP28 specifications as the Dell reference SKU. It operates plug-and-play in Dell switches and servers with QSFP28 and SFP28 ports.

Q: Which Dell platforms support this breakout cable?
A: This cable is compatible with Dell networking switches and servers featuring 100G QSFP28 ports on one end and 25G SFP28 ports on the other. Specific platform compatibility depends on the presence of QSFP28 and SFP28 port support and adherence to IEEE 802.3bj standards in the Dell equipment.

Q: Do the four 25G lanes operate independently or as a bonded group?
A: The four 25G lanes operate completely independently. Each of the four copper pairs connects one lane from the 100G QSFP28 end to a discrete 25Gbps SFP28 connector. Each SFP28 end can be inserted into a different switch or server port, allowing asymmetric topologies where one 100G port fans out to four separate 25G destinations.

Q: What is the difference in FEC support across the available lengths?
A: Cables up to 2M conform to IEEE 802.3by CA-25G-N (no FEC) and deliver the lowest latency. Cables 3M and longer conform to CA-25G-L and may require RS-FEC (Reed-Solomon Forward Error Correction) to maintain signal integrity at extended reach. The host switch must support and enable RS-FEC for 3M and 5M lengths if required by the link budget.

Q: Can I mix this passive DAC breakout cable with active optical breakout cables in the same fabric?
A: Yes. Both passive DAC and active optical (AOC) breakout cables terminate in standard QSFP28 and SFP28 form factors and comply with the same IEEE 802.3bj signaling specifications. The host switch treats them identically at the electrical interface. DAC is preferred for cost and latency within 5M; AOC extends reach beyond passive copper limits without concern for EMI or bend radius.